Method for the preparation of ethylenically unsaturated compounds with lactam-blocked isocyanate groups

ABSTRACT

The invention relates to a method for the preparation of ethylenically unsaturated lactam-blocked isocyanate compounds, by reacting an unsaturated amine-functional or hydroxy-functional compound with carbonylbislactam. These compounds can be polymerised and are subsequently cured by the built-in crosslinker to form thermosetting polymers which can be applied for instance in powder coatings.

The invention relates to a method for the preparation of ethylenicallyunsaturated compounds with one or more lactam-blocked isocyanate groups,which can be used for the preparation of (co)polymer compositions, whichcompositions can in turn be crosslinked to form network structures.

Isocyanates are commonly used as crosslinkers for polymers that containhydroxy groups in the polymer backbone, resulting in the formation of aurethane network. They are very reactive relative to nucleophiles, suchas for example alcohols, phenols and amines. This high reactivity doeshowever sometimes cause problems. Isocyanates are for example unstablein a moist environment. When used as a crosslinking agent prematuregelation in the extruder is the greatest problem. The reactivity can bereduced by protecting the isocyanate groups, hereinafter referred to asblocked isocyanate groups.

Blocked isocyanates have been known for some 50 years, but only duringthe last 20 years has the use thereof significantly increased. For adetailed literature survey of the applications of blocked isocyanates,see D. A. Wicks and Z. W. Wicks Jr, Blocked isocyanates III, Part B:Uses and applications of blocked isocyanates, Progress in OrganicCoatings 41:1-83 (2001), Elsevier Science B.V. These compounds areprepared conventionally by preparing first a isocyanate from thereaction of phosgene and a amine, after which a blocking agent is addedto protect the isocyanate group (—N═C═O). There is a large variety ofblocking agents; many isocyanates can be blocked excellently withcaprolactam (Wicks, as above, page 9 and 10). Caprolactam is cheap andfurthermore has a low toxicity. Only at higher temperatures doesdeblocking of the isocyanate group occur; in the case of caprolactam at175° C.

Ethylenically unsaturated compounds with blocked isocyanate groups aredescribed in the literature by for instance T. Sadoun c.s., Makromol.Chem. 188:1367-1373 (1987). These authors describe the preparation of2-isocyanatoethyl methacrylate, with the isocyanate group being blockedby phenol, propanone oxime, butanone oxime, benzophenone oxime orε-caprolactam (referred to hereinafter as caprolactam, unless otherwisestated), in one step, respectively the preparation in two steps of4-methyl-1,3-phenylene diisocyanate, with the first isocyanate groupbeing blocked by phenol or caprolactam and the second group by2-hydroxyethyl methacrylate.

Further, G. Clouet and T. Sadoun, in Pure Appl. Chem., A29:939-952(1992), describe the (co)polymerisation of 2-isocyanatomethacrylate,with the isocyanate groups being protected by phenol, propanone oxime,benzophenone oxime and caprolactam. These authors also indicate that byaddition of bifunctional compounds, such as diamines or dioles,three-dimensional systems can be formed.

A great disadvantage of the preparation of ethylenically unsaturatedblocked isocyanate compounds according to the prior art is that untilnow it has always been necessary to start from the correspondingunprotected isocyanate compounds, which are generally very toxic andexpensive. The toxicity of compounds such as 2-cyanatoethylmethacrylate[30674-80-7], H₂C═C(CH₃)C(O)OCH₂CH₂N═C═O, has been documented in detail.For these reasons ethylenically unsaturated blocked isocyanate compoundshave not been used until now for the preparation and curing of polymersof the category of hydroxy-functional poly(meth)acrylates orhydroxy-functional polyesters. Instead, these polymers were prepared inseparate steps and cured by addition of bifunctional compounds such asHDI (hexamethylene diisocyanate) or IPDI (isophorone diisocyanate) ortrimers hereof blocked with caprolactam. Adding a separate crosslinkerdoes not only mean an extra step in the preparation process, but alsohas the objection that the crosslinker cannot always be mixedhomogeneously with the relevant polymer resin.

The object of the invention is to provide a new method in which thisdisadvantage is avoided and ethylenically unsaturated lactam-blockedisocyanates are prepared in an environmentally friendly and efficientway.

According to another object of the invention polymers are provided ofthe poly(meth)acrylate type with a ‘built-in’ crosslinker, so that noextra mixing stage is necessary in the extruder and furthermore apossible mixing problem is avoided.

Surprisingly it was found that these objectives can be achieved bypreparing ethylenically unsaturated compounds with one or morelactam-blocked isocyanate groups, without starting from an isocyanatecompound, with an amine- or hydroxy-containing compound that contains atleast one second functional group being reacted with a carbonylbislactamcompound and the obtained blocked isocyanate compound, containing saidat least one second functional group, if this is a group other than avinyl group, being further converted into an ethylenically unsaturatedblocked isocyanate compound.

The invention therefore relates to a method for the preparation of anethylenically unsaturated blocked isocyanate compound with the generalformula (I):

in which

-   R is hydrogen or methyl-   X is a lactam group with formula (II):    in which-   n is a whole number from 3 to 15,-   Y is:    -   carbonyl,    -   phenyloxy (preferably 4-phenyloxy),    -   (CH₂)_(m), in which m is a whole number from 1 to 15 and the        alkylene group can be substituted by one or more C₁₋₆ alkyl        groups,    -   carbonyloxy(CH₂)_(m), in which m is a whole number from 1 to 15        and the alkylene group can be substituted by one or more C₁₋₆        alkyl groups,    -   carbonyloxy(CH₂)_(m)O(CH₂)_(p), in which m and p are each        separately a whole number from 1 to 15 and the respective        alkylene group can be substituted by one or more C₁₋₆ alkyl        groups,    -   (CH₂)_(q)carbonylaza, in which q is a whole number from 0 to 15        and the alkylene group can be substituted by one or more C₁₋₆        alkyl groups, and-   Z is a continuous bond or a carbonyl-(CH₂)_(n) group, in which n has    the above-mentioned meaning, characterised in that-   a) an amine-functional compound with formula (III):    in which R and Y have the above-mentioned meaning, or-   b) a hydroxy-functional compound with formula (IV):    in which R has the above-mentioned meaning and Y′ the same meaning    as Y, except carbonyl, is reacted with a carbonylbislactam compound    with formula (V):    in which n has the above-mentioned meaning.

Preferably carbonylbiscaprolactam (‘CBC’) is used as carbonylbislactamcompound. This implies that in the above compounds with the formulas(I), (II) and (V) the value of n is preferably 5.

In the method defined above for the preparation of ethylenicallyunsaturated blocked isocyanates with formula (I) two main types can bedistinguished: a) the reaction of an amine-functional compound with acarbonylbislactam compound with formula (V), with generally one of thelactam rings being split off, and b) the reaction of ahydroxy-functional compound with a carbonylbislactam compound withformula (V), with usually one of the lactam rings being opened. In thefirst case Z in formula (I) is a continuous bond, which means that informula (I) Z represents a bond connecting Y and N directly to eachother, and in the second case Z is a carbonyl alkylene group. In bothcases the remaining part of the carbonylbislactam compound according toformula (V) constitutes the desired blocked isocyanate group in thecompounds with formula (I), without use of an unblocked isocyanatecompound. Generally the reaction of the amine-functional compounds withcarbonylbislactam can be carried out without a catalyst, because thereactivity of the amine compounds to be used is usually adequate. Ifdesired a suitable catalyst can still be added to promote the reactionfurther. For the reaction of the less reactive hydroxy-functionalcompounds a catalyst generally is necessary however. Suitable catalystsare for instance acids and bases, including Lewis acids and Lewis bases.

Examples of acids, including Lewis acids, that are suitable as acatalyst are LiX, Sb₂O₃, GeO₂ en As₂O₃, BX₃, MgX₂, BiX₃, SnX₄, SbX₅,FeX₃, GeX₄, GaX₃, HgX₂, ZnX₂, AlX₃, TiX₄, MnX₂, ZrX₄, R₄NX, R₄PX, HX,where X═I, Br, Cl, F, OR, acetylacetonate, or a compound according toformula (a)

in which formula R″ and R′″ are independently chosen from the seriescomprising alkyl, aryl, alkoxy and aryloxy and R=alkyl or aryl.Brönstedt acids such as H₂SO₄, HNO₃, HX′ (where X′═I, Br, Cl, F), H₃PO₄,H₃PO₃, RH₂PO₂, RH₂PO₃, R[(CO)OH]_(n), where n=1-6 are also suitable.

Examples of (Lewis) bases which are suitable as a catalyst are: alkalior earth alkali metal hydrides, hydroxides, C₁₋₂₀ alkoxides andphenolates, NR″″_(n)H_(4-n)OH (R″″═C₁₋₂₀ alkyl or aryl), triamines, suchas triethylamine, tributylamine and trioctylamine, and cyclic amines,such as diazabicyclo[2,2,2]octane (DABCO), dimethylaminopyridine (DMAP),guanidine and morpholine.

A further aspect of the present invention, as an alternative to themethod of the invention, relates to first reacting an amine-functionalor a hydroxy-functional compound, which has furthermore at least onesecond functional group, with a carbonylbislactam compound according toformula (V), after which the resulting blocked isocyanate compound isfurther converted into an ethylenically unsaturated blocked isocyanatecompound with formula (I). The second functional group is chosen fromthe group of hydroxyl, amine at a secondary carbon atom, secondary amineand an unsaturated group. A suitable amine-functional compound with asecond functional group for example is hydroxyalkylamine, with thehydroxy group usually being terminal. This type of compound, theproduction of which is known or easily established for a person skilledin the art, reacts relatively quickly with carbonylbiscaprolactam (theamine group is more reactive than the hydroxy group, so that the desiredlink takes place in a predominant measure), after which the formedcompound with the hydroxy functionality is converted into the desiredcompound with formula (I). An example of this preferred reaction is thereaction of a terminal hydroxyalkylamine with CBC, followed by theconversion of the obtained compound with (meth)acrylic acid or areactive derivative thereof, for example the acid chloride, as isillustrated further in the examples 2a and 2b.

In a preferred method according to the present invention a compound withformula (I), in which X is a caprolactam group, Y a substituted orunsubstituted alkylene group and Z a continuous bond, is prepared byreacting the corresponding unsaturated alkylamine with CBC. An exampleof this reaction is the reaction of allylamine with CBC according to thefollowing reaction equation:

In another preferred method according to the present invention acompound with formula (I) is prepared, in which X is a caprolactamgroup, Y a carbonyl group and Z a continuous bond, by reacting thecorresponding (meth)acrylamide with CBC. An example of this reaction isrepresented by the following reaction equation:

In yet another preferred method according to the present invention acompound with formula (I), in which X is a caprolactam group, Y asubstituted or unsubstituted carbonyloxyalkyelene group and Z anoxycarbonyl(C₅)alkylene group, is prepared by reacting the correspondinghydroxyalkyl(meth)acrylate compound with CBC. An example of thisreaction is represented by the following reaction equation:

According to an alternative embodiment of the method for the preparationof a compound with formula (I) according to the present invention firstan intermediate product is prepared by reacting an amine-functional or ahydroxy-functional compound, which furthermore comprises at least onesecond functional group but no unsaturated bond, with acarbonylbislactam compound according to formula (V), after which theobtained blocked isocyanate compound is further converted into anethylenically unsaturated blocked isocyanate compound with formula (I).

Other compounds with formula (I), which have not been described indetail herein, can be prepared by a person skilled in the art withoutproblems in a way known for the synthesis of analogous compounds, withthe help of the present specifications and further with application ofthe general and specific knowledge of the person skilled in the art inthis field.

The reaction conditions for the execution of the method according to theinvention are not especially critical and can therefore be chosen by theperson skilled in the art within fairly broad limits. Usually thereactions are carried out in a suitable solvent at a temperature whichis chosen within broad limits and usually lies between room temperatureand the boiling temperature of the solvent. A suitable solvent is forexample toluene or xylene, with a reaction temperature which preferablylies in the range of 50-150° C., more preferably in the range of 70-150°C. The reaction time with the said solvent and the said reactiontemperature is approximately 1 to 3 hours for the reaction of CBC withan amine-functional compound and approximately 3 to 5 hours for acompound with a hydroxy-functional compound.

The reactions can also be carried out without solvent in a melt of thereaction components, with the components being mixed, for example in asuitable reactor. In that case the reaction temperature preferably liesin the range of 100-150° C. and the reaction time is preferably 1 to 3hours.

The preparation of the carbonylbislactam to be used, for example byreaction of the relevant lactam with phosgene, is described in theliterature. See for example WO-A-98/47940. The preparation of N,N′-carbonylbiscaprolactam in benzene in the presence of a tertiaryalkylamine as acid scavenger, is described for example in JP-A-42017832.Carbonylbiscaprolactam is commercially obtainable from DSM in Geleen,the Netherlands.

The preparation of the other starting materials described above is knownfrom the literature or can be performed by a person skilled in the artin a way known for the preparation of analogous compounds.

The invention further relates to a thermosetting copolymer whichcontains more than one lactam-blocked isocyanate group and also at leasttwo functional groups of the hydroxy and/or amine type per unit. Thesecan be for example (co)polymers of the type of poly(meth)acrylates,which can be prepared in suitable way by (co)polymerisation of theabove-defined ethylenically unsaturated compounds with one or morelactam-blocked isocyanate groups according to formula (I). For thecopolymerisation compounds of the type of hydroxyalkyl(meth)acrylates,alkyl(meth)acrylates and/or styrene are very suitable. Due to thebuilt-in lactam-blocked isocyanate groups in the compounds with formula(I) no separate crosslinker needs to be added for curing and thepolymers can be cured without further additives whether or notimmediately after the formation of the polymers by raising thetemperature. A further advantage of the application of thelactam-blocked isocyanates according to the invention is that ascrosslinkers these bring about no or only a small reduction of the glasstransition temperature, which is important especially for theapplication in powder coatings.

Preferably the polymerisation takes place at a temperature in the rangeof 50 to 100° C. The reaction time of the polymerisation is alsodependent on the type of initiator and is usually 2 to 10 hours. Thecuring is usually carried out at a temperature of 150-200° C. and thecuring time usually is of the order of 10 to 30 minutes.

The polymers according to the invention can be applied for many kinds ofpurposes. Preferably they are applied in powder coatings. For thespecific applications the usual additives such as pigments and flowagents can be added as desired during or after the preparation of thepolymers.

The invention is now illustrated further by the following examples,which are intended exclusively as illustration of the invention and notto limit the invention in any way.

EXAMPLE 1

Reaction of Allylamine with Carbonylbiscaprolactam

In a 250 ml flask, provided with a cooler, 5 g CBC (0.02 mole) wasdissolved in 50 ml ethyl acetate (10% solution) at 50° C. A solution of5.70 g allylamine (0.1 mole) in 50 ml ethyl acetate was added dropwise.With thin-layer chromatography (TLC; eluent ethylacetate:hexane 1:4;Rf_(CBC)=0.17 and Rf_(product)=0.32) it was established that after anight of reaction the CBC was completely converted. The solution wasshaken out three times with a saturated aqueous NaCl solution to removethe excess allylamine and the formed caprolactam. The organic layer wasdried with sodium sulphate. After removal of the sodium sulphate byfiltration the solution was concentrated on a falling-film typeevaporator. The yield of the desired product amounted to 2.5 g (65%).

¹H-NMR (CDCl₃) δ: 1.5-1.8 (b, 6H, —CH₂—), 2.6-2.8 (m, 2H, —CH₂—C═O),3.7-4.0 (m, 4H, —CH₂—NH en —CH₂—N—C═O), 5.0-5.2 (m, 2H, C═CH₂), 5.7-5.9(m, 1H, ═CH—CH₂), 9.1-9.5 (b, 1H, NH).

EXAMPLE 2a

Reaction of Propanolamine with Carbonylbiscaprolactam, by Conversionwith Acryloyl Chloride

7.5 g (0.1 mole) propanolamine and 25.2 g (0.1 mole)carbonylbiscaprolactam were dissolved in 100 ml toluene. The solutionwas heated during 5 hours at 70° C. The mixture was cooled down to roomtemperature, after which 9.1 g (0.1 mole) acryloylchloride (X═Cl, in theabove reaction) and 10.1 g (0.1 mole) triethylamine were added. Themixture was kept at 20° C. for 4 hours. The caprolactam andtriethylamine.HCl salt, which had been released during the reaction,were removed by extracting the mixture twice with 50 ml water. Theproduct was isolated by distilling toluene off at 90° C. and 25 mbarpressure.

EXAMPLE 2b

Example 2a was repeated with acrylic acid instead of acryloyl chloride.Thus, 7.5 g (0.1 mole) propanolamine and 25.2 g (0.1 mole)carbonylbiscaprolactam were dissolved in 100 ml toluene. The solutionwas heated for 5 hours at 70° C. Hereafter 7.2 g (0.1 mole) acrylicacid, 0.25 g hydroquinone monomethylether and 0.25 g p-toluenesulfonicacid were metered in. The mixture was heated to 120° C. and the waterwas distilled off azeotropically for 4 hours. The mixture was cooleddown to room temperature and extracted twice with 50 ml water. Themonomer was isolated by distilling toluene off at 90° C. and 25 mbarpressure.

EXAMPLE 3

13 g (0.1 mole) hydroxyethylmethacrylate, 25.2 g (0.1 mole)carbonylbiscaprolactam, 0.25 g Zr(OBu)₄ and 0.025 g hydroquinonemonomethylether were heated in a three-neck flask in a nitrogenatmosphere to 120° C. The reaction was ended after three hours and themixture was analysed subsequently with IR and ¹H NMR. The mixturecontained 81 wt % of the blocked isocyanate compound according to thestructure as mentioned in the introduction of this example.

EXAMPLE 4

Copolymerisation of Hydroxy Ethylacrvlate (HEA), Methylacrvlate (MA) andCaprolactam Blocked Isocyanopropylacrvlate (C-BIPA)

Polymerisations were carried out in a three-neck flask, provided with astirrer and a nitrogen purge. Tetrahydrofuran (THF), which was used assolvent, had been dried previously on NaH. The monomers, as specified inTable 1, were polymerised in different ratios in 250 ml THF undernitrogen, with AIBN (azoisobutyronitrile) as initiator. For thispolymerisation the ratio of the monomer relative to the initiator is50:1.

The different compositions produced are shown in the the followingTable 1. TABLE 1 Composition of the copolymer quantity quantity quantityquantity quantity quantity quantity quantity Monomer (Mol %) (g) (Mol %)(g) (Mol %) (g) (Mol %) (g) MA  95% 16.34 g  90%  15.51 g   85% 14.63 g 80% 13.76 g  HEA 2.5% 0.60 g 5% 1.15 g 7.5% 1.73 g 10% 2.22 g (C-BIPA)2.5% 1.38 g 5% 2.66 g 7.5% 4.05 g 10% 5.36 gThe polymers were isolated by evaporating the solvent THF at 50° C.

EXAMPLE 5

Copolymerisation of Hydroxyethyl Methacrylate (HEMA), MethylMethacrylate_(MMA) and Caprolactam Blocked Isocyanopropylacrylate(C-BIPA).

Polymerisations were carried out in a three-neck flask, provided with astirrer and a nitrogen purge. Tetrahydrofuran (THF), which was used assolvent, was previously dried on NaH. The monomers, as specified inTable 2, were polymerised in 250 ml THF under nitrogen with AIBN asinitiator. For these polymerisations the ratio of monomer relative tothe initiator is 50:1. The different compositions produced are shown inthe following Table 2. TABLE 2 Composition of the copolymer quantityquantity quantity quantity quantity quantity quantity quantity Monomer(Mol %) (g) (Mol %) (g) (Mol %) (g) (Mol %) (g) MMA  95% 19.33 g  90% 18.12 g   85% 17.05 g  80% 16.04 g  HEMA 2.5% 0.65 g 5% 1.30 g 7.5% 2.00g 10% 2.66 g (C-BIPA) 2.5% 1.35 g 5% 2.72 g 7.5% 4.15 g 10% 5.43 g

EXAMPLE 6

Gel Experiments

Gel experiments are indicative of the crosslink behaviour of the coatingresins. Gel experiments were carried out with approximately one gram ofcopolymer. The catalyst, dibutyltin dilaurate (see table for mass %),was added as a solution in THF to the polymer, after which the solventwas removed by heating. The polymer was heated to 180° C. and the gelpoint was determined as the moment when the product behaves no longer asa melt, but becomes a lump. The results are presented in Table 3. TABLE3 Results of gel experiments Incorporation Required cross- specificationAmount of catalyst linking time (mol % HEA) (mass %) (seconds) 2.5 1 3302.5 0.5 250 2.5 0.1 280 2.5 0 510 5.0 1 185 5.0 0.5 150 5.0 0.1 225 7.51 105 7.5 0.5 110 7.5 0.1 100 10 1 195 10 0.5 204 10 0.1 252

The table suggests that the gel times are of the order of 2-10 minutes.This is in agreement with what is expected of a good crosslinkingsystem.

1. Method for the preparation of an ethylenically unsaturated blockedisocyanate compound with the general formula (I):

in which R is hydrogen or methyl X is a lactam group with formula (II):

in which n is a whole number from 3 to 15, Y is: carbonyl, phenyloxy(preferably 4-phenyloxy), (CH₂)_(m) in which m is a whole number from 1to 15 and the alkylene group can be substituted by one or more C₁₋₆alkyl groups, carbonyloxy(CH₂)_(m), in which m is a whole number from 1to 15 and the alkylene group can be substituted by one or more C₁₋₆alkyl groups, carbonyloxy(CH₂)_(m)O(CH₂)_(p), in which m and p are eachseparately a whole number from 1 to 15 and the respective alkylene groupcan be substituted by one or more C₁₋₆alkyl groups,(CH₂)_(q)carbonylaza, in which Q is a whole number from 0 to 15 and thealkylene group can be substituted by one or more C₁₋₆ alkyl groups, andZ is a continuous bond or a carbonyl-(CH₂)_(n) group, in which n has theabove-mentioned meaning, wherein a) an amine-functional compound withformula (m):

in which R and Y have the above-mentioned meaning, or b) ahydroxy-functional compound with formula (IV):

in which R has the above-mentioned meaning and Y′ the same meaning as Y,except carbonyl, is reacted with a carbonylbislactam compound withformula (V):

in which n has the above-mentioned meaning.
 2. Method according to claim1, wherein carbonylbiscaprolactam is used as carbonylbislactam compound.3. Method for the preparation of an ethylenically unsaturated blockedisocyanate compound with the general formula (I):

in which R, X, Y and Z have the meaning defined in claim 1, wherein anamine-functional or a hydroxy-functional compound, which furthercomprises at least one second functional group chosen from the group ofhydroxyl, amine at a secondary carbon atom and secondary amine but nounsaturated bond, is reacted with a carbonylbislactam compound accordingto formula (V),

after which the obtained blocked isocyanate compound is furtherconverted into an ethylenically unsaturated blocked isocyanate compoundwith formula (I).
 4. Method according to claim 1, wherein a compoundwith formula (I) is prepared, in which X is a caprolactam group, Y asubstituted or unsubstituted alkylene group and Z said continuous bond,by reacting the corresponding unsaturated alkylamine withcarbonylbiscaprolactam.
 5. Method according to claim 1, wherein acompound with formula (I) is prepared, in which X is a caprolactamgroup, Y a carbonyl group and Z said continuous bond, by reacting thecorresponding (meth)acrylamide with carbonylbiscaprolactam.
 6. Methodaccording to claim 1, wherein a compound with formula (I) is prepared,in which X is a caprolactam group, Y a substituted or unsubtitutedcarbonyloxyalkyelene group and Z an oxycarbonyl(C₅)alkylene group, byreacting the corresponding hydroxyalkyl(meth)acrylate compound withcarbonylbiscaprolactam.
 7. Method according to claim 3, wherein acompound with formula (I) is prepared, in which X is a caprolactamgroup, Y a substituted or unsubtituted carbonyloxyalkyelene group and Zsaid continuous bond, by reacting a substituted or unsubtitutedalkylamine compound, which has at least one second functional group,chosen from the group of hydroxyl, amine at a secondary carbon atom,secondary amine and an unsaturated group, with carbonylbiscaprolactamand thereby converting the obtained lactam-blocked isocyanate compoundinto an ethylenically unsaturated lactam-blocked isocyanate.
 8. Methodaccording to claim 7, wherein the alkylamine compound with a secondfunctional group is hydroxyalkylamine and the obtained lactam-blockedisocyanate compound is converted with (meth)acrylic acid into anethylenically unsaturated lactam-blocked isocyanate compound.